The Reactivity of the Antibiotic Sesquiterpene Isovelleral Towards Primary Amines1

The comparison of the antibiotic activity of isovelleral (1) and the two synthetic compounds 3 and 4 with data from molecular mechanics calculations, suggest that the reaction of isovelleral with amines to form pyrrole derivatives, as previously has been observed with the dialdehyde polygodial (2), may be responsible for its bioactivities. Isovelleral (1) was found to react with 1,3-diaminopropane in ethanol, and a pyrrole derivative was isolated and characterised. However, the reaction was slow and several other products were also formed, and polygodial (2), which is as antibiotic as 1, reacts more than 100 times faster with propylamine and lysine. It is therefore unlikely that the reaction with primary amines to form pyrrole derivatives is responsible for the antibiotic activity of isovelleral (1).